Effects of Repeated 131I-meta-iodobenzylguanidine Radiotherapy on Tumor Size and Tumor Metabolic Activities in Patients with Metastatic Neuroendocrine Tumors

131I-meta-iodobenzylguanidine (131I-MIBG) radiotherapy has shown some survival benefits in metastatic neuroendocrine tumors (NETs). European Association of Nuclear Medicine (EANM) clinical guidelines for 131I-MIBG radiotherapy suggest a repeated treatment protocol, although none currently exists. The existing single-high-dose 131I-MIBG radiotherapy (444 MBq/kg) has been shown to have some benefits for patients with metastatic NETs. However, this protocol increases adverse effects and it requires alternative therapeutic approaches. Therefore, the aim of this study was to evaluate the effects of repeated 131I-MIBG therapy on tumor size and tumor metabolic response in patients with metastatic NETs